The objectives of the program project proposal are to utilize nutritional manipulations to chronologically delay aging in rats and to analytically probe the aging process in those animals. These objectives are based on our hypothesis that nutritional manipulations, such as lifelong postweaning food restriction, prolong life span by attenuating age-related physiologic decline. Since our initial studies have yielded data in support of this hypothesis, the aim of this proposal is to pursue the concept further by expanding the scope of physiologic activities to be studied and by exploring a variety of nutritional manipulations which differ in their quantitative, qualitative and temporal nature. The program includes eight projects designed to investigate the effects of these nutritional manipulations on the following biological phenomena: longevity, age of onset and the nature of age-related diseases, age-related changes in adipose tissue physiology, age-related changes of certain key metabolic and hormonal components of blood serum, age-related changes of aspects of hepatic lipid metabolism, age-related changes in skeletal muscle function, age-related changes in the functional properties of arteries and aspects of age-related bone loss.